1. Technical Field of the Invention
The present invention relates to an air compressor and, more particularly, to an air compressor that includes an audible alarm device mounted to an outlet of a storage container thereof for producing a high-frequency sound for alerting users when compressed air produced in a cylinder thereof exceeds a predetermined value, wherein the sliding cap of the audible alarm device can be driven by the compressed air to perform a quick, slight back-and-forth movement of high frequency, so that the sliding cap can be partially moved out of the opening of an external enclosure thereof and thus exposed to the outside.
2. Description of the Prior Art
In early period, the air storage container used in air compressors is only provided with two outlet tubes or ducts, one of which can be connected with a pressure gauge and the other of which can be connected with a hose for inflating an object. For improving the function of an air compressor, a multi-duct air compressor, U.S. Pat. No. 7,462,018 issued to the applicant, was disclosed. In the patent, the air storage container is provided with multiple ducts, wherein one of the ducts can be installed with a pressure gauge while the rest of the ducts can be installed with a safety valve which allows the air within the air storage container or the cylinder to be released automatically, when the air pressure exceeds a predetermined value, to protect the operation of inflating objects. Alternatively, one of the ducts can be installed with a manually-operated relief valve; therefore, when overpressure occurs, a user may operate the relief valve to release the air within the storage container or the cylinder, so that the object to be inflated can be prevented from damages due to overpressure.
To enable users to know the air pressure in the storage container or the cylinder, most of existing air compressors are equipped with a round-boxed pressure gauge, which employs a pointer driven by various mechanical elements. However, it is difficult for a user to identify the reading value of the pressure gauge when working in a dark environment or at nights. Furthermore, although the air compressor is equipped with a pressure gauge for providing a visual indication, the user cannot recognize an overpressure condition of the air compressor when the gauge is incidentally failed; in this case, the air compressor may unduly inflate an object, thereby causing damages to the object. Even though one of the ducts is installed with a safety valve for protecting the operation of inflating objects, the cost of the air compressor will be increased accordingly. Besides, after a long-period use, the safety valve may fail; thus, when inflating a tire, the tire may be overly inflated, which may cause a blowout, or the air compressor may be overheated or failed.
In view of the foregoing, for solving the problems of the existing air compressors wherein the pressure gauge cannot alert users to overpressure in any circumstances, and the incorporation of a safety valve will increase the cost of an air compressor, the applicant has contrived a novel air compressor, which can alert a user to an overpressure condition through an audible alarm device without installing a safety valve.